En este informe se presenta la transcripción de la sesión realizada el 6 de mayo de 1991, en la que se estudió la ponencia sobre planeación.

En este informe se encuentra la transcripción de la sesión plenaria realizada el 4 de julio de 1991 y el texto de la Constitución Política de Colombia publicada en la Gaceta Constitucional número 116, del 20 de julio.

Nordic countries experience post-glacial rebound, a movement where geographical contours slowly change elevation with respect to the mean sea level. The glacial isostatic adjustment (GIA) model aims to explain the phenomena, which combined with seismic data allows geoscientists to reconstruct elastic coefficients and viscosities of the Earth's lithosphere and upper mantle. The use of standard commercial codes are not adequate for GIA simulations and result in significant errors in the displacement field. This negative outcome suggests the development of GIA codes that include advection of pre-stress in the model. The problem set up consists on a solid 2D elastic layer under a flat Earth approximation, described by three different models suggested by current studies in geophysics.For space discretization the mixed finite element method (mFEM) is used and efficient preconditioners are built for the resulting algebraic system in saddle point form. A three level GMRES iterative solution strategy is proposed, based on Schur Complement preconditioners coupled with Multigrid techniques. The implementation is presented as a ready-to-use toolbox that easily deals with problem parameters, geometries, compressible and fully incompressible materials and provides higher accuracy for the displacement field compared with the previously existent codes. It also can be easily extended to 3D geometries and allows the implementation of a viscoelastic mantle. The code is written in C++ using the deal.II library designed for FEM, permitting the use of readily-made software packages, such as Trilinos that are straightforwardly parallelizable.

Abstract: The synthesis of nanostructures has attracted much interest due to their advanced properties compared to their bulk material. Zinc Oxide (ZnO) has gained substantial interest in the research community due to its large exciton binding energy (60 meV). ZnO is a semiconductor with several favorable properties like a good transparency in the visible region, and a wide band gap of 3.37 eV. Those properties are already used in many emerging applications as chemical sensors, nano laser, and transistors. Due to its wurtzite crystal structure ZnO readily grows to elongated nanoparticles such as nanorods or nanowires. Elongated nanostructures are promising due to precise electron transport in one direction. Special attention has been devoted to the realization of transparent conductive oxides (TCOs) for optoelectronic devices such as solar cells and displays. The first part of this thesis is dedicated to the comparison of the synthesis of ZnO nanorods in a three-neck flask to solvothermal method. In order to investigate the effects of various reaction parameters on the structural and optical properties in the solvothermal method, different temperatures, volumes of solvent and reaction time were selected. The second part addresses the tailoring of the microstructure and electrical properties of ZnO nanorods modified with aluminum and indium, respectively. Finally, doped ZnO nanorods thin films prepared on glass substrate by drop casting method were investigated. This thesis provides first experimental work for transparent conductive zinc oxide prepared by solvothermal synthesis and highlights possibilities and boundaries for introduction of dopants in ZnO nanorods. Resumen: La síntesis de nanoestructuras ha atraído mucho interés debido a sus excelentes propiedades en comparación con su material a granel. El óxido de zinc (ZnO) ha ganado un interés sustancial en la comunidad de investigación debido a su gran energía de ligadura (60 meV). ZnO es un semiconductor con varias propiedades favorables, así como una buena transparencia en la región visible, y una amplia brecha de banda de 3,37 eV. Esas propiedades ya se utilizan en muchas aplicaciones emergentes como sensores químicos, nano láser y transistores. Debido a su estructura de cristal de wurtzita, ZnO se desarrolla fácilmente a nanopartículas alargadas como nanorods o nanocables. Las nanoestructuras alargadas son prometedoras debido al transporte preciso de electrones en una dirección. Se ha dedicado especial atención a la realización de óxidos conductores transparentes (TCO) para dispositivos optoelectrónicos como células solares y pantallas. La primera parte de esta tesis está dedicada a la comparación de la síntesis de nanorods de ZnO en un matraz de tres bocas versus un método solvotermal. Con el fin de investigar los efectos de diversos parámetros de reacción sobre las propiedades estructurales y ópticas en el método solvotermal, se seleccionaron diferentes temperaturas, volúmenes de disolvente y tiempo de reacción. La segunda parte aborda la adaptación de la microestructura y las propiedades eléctricas de los nanorods de ZnO modificadas con aluminio e indio, respectivamente. Finalmente, se investigaron las películas finas de nanorods modificadas y preparadas sobre sustrato de vidrio mediante el método de moldeo a gotas. Esta tesis proporciona el primer trabajo experimental para óxido de zinc como conductor transparente preparado por síntesis solvotérmica y resalta las posibilidades y los límites para la introducción de dopantes en nanorods de ZnO.

The need of understanding the relationship between the physical habitat and ecology in the fluvial systems has become a major issue due to an increasing environmental conciousness but also because of the normativity which demand the achievement of the good status of the water bodies and its ecosystems. Exactly this requirement is prescribed by the European Water Framework Directive (WFD) which have included the hydromorphology as an important aspect of evaluation due to the influence that it has on the ecology of a river system. The hydromorphology gets relevance because it study the system as a whole, involving the interactions between ecology, hydrology and fluvial geomorphology. As a response to the WFD each country of the European Union has developed a method for guaranteeing the compliance of the normativity. Elements of such methods and of international literature are collected for the development of a methodology that fulfill the gaps of the current Colombian water normativity and support the decision making in the environmental planning and impact assessment. This guide for the river morphological restoration in Colombia is a complete hydromorphological analysis of a selected river which main purpose is to make an approach to the general aspects of the river in the macro scale, followed by an assessment in the meso scale in which the river is segmented, classified and the hydromorphological conditions are scored; finally, a simulation is performed for a critical reach, called in this work the “bottle neck” reach. The simulation consists in a hydrodynamics model (or hydromorphodynamics model as optional), its results of depth, velocity and substrate in combination with the preferences of a fish indicator species, are computed in the software CASiMiR and give the habitat suitability in the study area for the simulated conditions. The application of such methodology is applied in a mountainous river reach downstream the Punt da Gall dam in Switzerland for which the hydromorphological aspects in the macro and meso scale are assessed and in the micro scale the habitat distribution of fish indicator species are calculated. The present work is an attempt to apply the habitat simulation as a tool for determining hydromorphological quality, for river restoration activities and for determining minimum habitat conditions when the discharge is regulated. Future investigations include the application in a Colombian river for which the collection of biological data still is a challenge.

This research is focused on obtaining an important reduction in greenhouse gas (GHG) emissions resulting from the use of fossil fuels by increasing the efficiency of pre-combustion carbon capture. It examines a new, low-risk, approach that uses conventional water gas shift reactors and acid gas removal technology in a unusual arrangement, within an Integrated Gasification Combined Cycle power plant (IGCC). Timmins (2010) proposed a flowsheet of this nature and it is this flowsheet that is used as the starting point for this research project. Process simulation in UniSim Design R390 is conducted  to validate the viability of such  a flowsheet and to investigate optimal plant configuration. The modelling output is compared to US DOE baseline studies for competing technologies (2010).The physical solvent, Selexol, is used for cardon dioxide (CO2) absorption as recommended by researchers as the most energy efficient amongst the range of physical and chemical solvents investigated. There are mainly two thermodynamic models required to meet all of the needs of this complex process. Most of the process is modelled with the Peng-Robinson equation of state but the Selexol absorber and desorber is modelled using the non-random-two-liquid model  (NRTL) for the liquid phase and the ideal gas law for the vapour phase. A beseline flowsheet model is successfully modelled that could be attached to an IGCC plant to enable it to continue producing electric power whilst capturing 90% of the carbon derived from the fuel. The model is used for process development, and for energy efficiency evaluation. Every major item of capital equipment has been included, modelled and sized to produce a cost analysis and additionallly, the model output was used for a preliminary life cycle analysis (LCA). From the results produced in this study, the proposed process appears to be a feasible, energy-efficient, alternative technology for incorporating carbon capture within an IGCC flowsheet.

On average, 44% of total water abstraction in Europe is used in agriculture. Evidence of water scarcity in Europe is borne out by research that shows increasing strain on water resources in 30% of EU member states. Current research seems to validate the view that wastewater treatment and reuse is a technical opportunity to address the imbalances between agricultural water demand and European water resources in the long term. Currently, just 2.4% of wastewater treatment plant (WWTP) effluents are reused, and thus the water reuse potential in Europe remains high. This document reports on and analyses the performance of a prototype-scale plant installed to treat real wastewater in rural Spain using a Treat & Reuse Membrane Bioreactor (T&R MBR). It shows that the T&R MBR is an improvement on MBR operations due to the fact that it produced a solids-free, nutrient rich and high-quality permeate in which Escherichia Coli was removed to values < 1 ufc/100ml. Furthermore, Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Turbidity and Suspended Solids (SS) were typically lowered to concentrations below the legal limit established in countries such as France, Italy, Spain, Greece, Cyprus and Portugal. Additionally, the system was able to extract nutrients from the wastewater inflow and to retain them in the permeate at 80% and 60% of the Nitrogen (once transformed to Nitrates) and Phosphorous, respectively. These results, combined with the continuing reduction of capital and operating costs for the T&R MBRs, suggest that they are an increasingly cost-effective technology for producing treated effluents suitable for water reuse in agriculture. This study also suggests possible limitations regarding the fate of micro-pollutants during treatment. Nevertheless, the system works efficiently so long as the wastewater input meets the typical composition of raw municipal wastewater with minor contributions of industrial wastewater. This would imply low concentration of trace organic contaminants (TrOCs) and Heavy Metals, as well as slight to moderate salinity (i.e. 0.7-3.0 dS/m). In spite of the fact that the T&R MBR technology can reduce the fresh water and fertilizer consumption of the agriculture sector, this system cannot be implemented in countries where the legislation restricts the reuse of effluents with significant concentrations of Nitrates and Phosphorous (e.g., Germany). Therefore, the present document suggests a set of technical criteria addressing the European challenges regarding water reuse in agriculture.

Tesis de Nicolás Osorio para optar al título de Doctor en Medicina, en la Facultad de Medicina de París, en 1865. A lo largo del documento, escrito en francés, Osorio analiza el comportamiento de los tumores que obstruyen el líquido cefalorraquídeo.

Adaptable Morphodynamics addresses the development of complex high density urban systems over space and time. Building morphologies can be conceived as living organisms that change in form, shape and structure through the interaction of physical, informational and geometrical processes. This research focuses on density, environmental quality and spatial identity. These studies are extended to present-day Hong Kong and addresses a design system that aims to reinterpret spatial logics, connected with local socio-cultural attributes, into a set of rules and code for an “intelligent densification”. From the data gathered, two strategies are developed in parallel and as they become more defined, they begin to inform one another until a holistic urban approach is developed. Urban porosity and Urban growth at different scales (neighbourhood, plot and building) become the key design tools to achieve environmental performance, in terms of urban ventilation, housing public programmes, and maximizing pedestrian and bicycle accessibility for all people through a fluid mobility network at ground and multiple layers of connectivity. Existing building morphologies are transformed computationally into porous organisms and are used to construct accurate models of growth for regaining the lost demographic pressure. Multi-objective evolutionary algorithms are employed to generate a complex urban design model. This is characterized by the emergence of public green areas, integration of socio-cultural amenities within the existing building morphologies and by generation of a comfortable outdoor microclimate, at different operational scales. The improvement of the well-being of the urban population could be achieved through a spatial approach based on principles of social inclusion, especially in the most deprived areas of the patch, characterized by illegal and informal settlements, known as “rooftop villages or sky-slums”. The main target, in the long term, will be to develop an “urban intelligence” that takes into account the mutual relation between demographic demand, site constraints and the potentialities and limitations of the architectural targets.

Recent projections estimate that the Netherlands needs circa 33 GW of offshore wind capacity in the North Sea to meet the goals of the Paris Agreement. To this end, the Dutch government has very ambitious plans to create new wind sites far from shore and integrate that power generation to the high-voltage power grid in the next years. Due to the challenges of connecting future massive amounts of offshore wind power into the grid TenneT operates it becomes urgent to investigate new alternatives for this purpose. A grid topology with transmission capacities above 1 GW connecting offshore wind farms at distances close to 100 km in a standardized, modular, and cost-efficient manner is the focus of this thesis. With eight point-to-point HVDC links in operation in Germany and more expected in near future, TenneT TSO is analysing new offshore grid connection concepts to achieve a reliable and secure operation of the infrastructure connecting wind energy both in Germany and the Netherlands. A solution is presented in this thesis report in which new wind farms are connected with 66-kV cables to a centralised platform with a connection capacity of 1050 MW. This platform will utilise HVDC technology based on VSC conversion techniques and MMC topology. It is expected that the 66-kV cables will not be connected to a single busbar through paralleled converter transformer, but that this will be done with at least three converter transformers connected to each other on the valve side but not connected on the 66-kV side. A dynamic performance study of a test network with the novel connection topology developed in PSCAD has been done. Each component of the system was studied to obtain a complete overview and understanding of the overall behaviour. All the associated control loops for the MMC terminals and wind turbines were modelled in detail. Through several simulations based on eight cases and scenarios the performance of the offshore 66-kV ac grid and the MMC-HVDC link using the control schemes of MMC converters as in a typical grid connection topology for OWFs was assessed. Proyecciones recientes estiman que los Países Bajos necesitan alrededor de 33 GW de capacidad eólica marina en el Mar del Norte para cumplir los objetivos del Acuerdo de París. Para este fin, el gobierno holandés tiene planes muy ambiciosos de crear nuevas plantas eólicas lejos de la costa e integrar esa generación de energía a la red eléctrica de alto voltaje en los próximos años. Debido a los desafíos de conectar cantidades masivas de energía eólica marina a la red que opera TenneT en el futuro, es urgente investigar nuevas alternativas para este propósito. El objetivo de esta tesis es estudiar una nueva topología de red con capacidades de transmisión por encima de 1 GW que conecte parques eólicos marinos a distancias cercanas a 100 km de manera estandarizada, modular y rentable. Con ocho enlaces HVDC punto a punto en operación en Alemania y más esperados en el futuro cercano, TenneT TSO está analizando nuevos conceptos de conexión a la red en el mar para lograr una operación confiable y segura de la infraestructura que conecta la energía eólica tanto en Alemania como en los Países Bajos. En este reporte de tesis se presenta una solución en la que los nuevos parques eólicos están conectados con cables de 66 kV a una plataforma centralizada con una capacidad de conexión de 1050 MW. Esta plataforma utilizará tecnología HVDC basada en las técnicas de conversión VSC con topología MMC. Se espera que los cables de 66 kV no se conecten a un solo punto eléctrico a través de transformadores convertidores en paralelo, sino que esto se hará con al menos tres transformadores convertidores conectados entre sí en el lado del convertidor, pero no en el lado de 66 kV. En este documento se presentan los resultados de un estudio dinámico de una red de prueba con la nueva topología de conexión desarrollada en PSCAD. Cada componente del sistema se estudió para obtener una visión general completa y una comprensión del comportamiento de toda la red. Todos los lazos de control de las estaciones convertidoras MMC y las turbinas eólicas se modelaron en detalle. A través de varias simulaciones basadas en ocho casos y escenarios se evaluó el comportamiento de la red de ac de 66 kV en alta mar y el enlace MMC-HVDC utilizando los esquemas actuales de control de los convertidores MMC de las topologías típicas de conexión de red para granjas eólicas marinas.